Lighting control having an idle state with wake-up upon actuation

ABSTRACT

A load control device for controlling the amount of power delivered from an AC power source to an electrical load, the load control device comprising a bidirectional semiconductor switch operable to be coupled in series electrical connection between the source and the load, the semiconductor switch having a control input; a controller operatively coupled to the control input of the semiconductor switch for controlling the amount of power delivered to the load; an actuator operatively coupled to the controller such that the controller is operable to determine a desired amount of power to be delivered to the load in response to actuations of the actuator; and a visual display responsive to the controller; wherein the controller is operable to illuminate the visual display to a first intensity upon actuation of the actuator and to subsequently illuminate the visual display to a second intensity less than the first intensity after a predetermined amount of time has elapsed since the actuation of the actuator.

CROSS-REFERENCE TO RELATED APPLICATION

This is a continuation of U.S. patent application Ser. No. 11/472,246,filed June 20 entitled LIGHTING CONTROL HAVING AN IDLE STATE WITHWAKE-UP UPON ACTUATION.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to load control devices for controllingthe amount of power delivered to an electrical load from a power source.More specifically, the present invention relates to a dimmer having aplurality of status indicators that illuminate to a dim level after apredetermined amount of time of inactivity.

2. Description of the Related Art

A conventional two-wire dimmer has two terminals: a “hot” terminal forconnection to an alternating-current (AC) power supply and a “dimmedhot” terminal for connection to a lighting load. Standard dimmers useone or more semiconductor switches, such as triacs or field effecttransistors (FETs), to control the current delivered to the lightingload and thus to control the intensity of the light. The semiconductorswitches are typically coupled between the hot and dimmed hot terminalsof the dimmer.

Smart wall-mounted dimmers include a user interface typically having aplurality of buttons for receiving inputs from a user and a plurality ofstatus indicators for providing feedback to the user. These smartdimmers typically include a microcontroller or other processing devicefor providing an advanced set of control features and feedback optionsto the end user. An example of a smart dimmer is described in greaterdetail in commonly assigned U.S. Pat. No. 5,248,919, issued on Sep. 28,1993, entitled LIGHTING CONTROL DEVICE, which is herein incorporated byreference in its entirety.

FIG. 1 is a front view of a user interface of a prior art smart dimmerswitch 10 for controlling the amount of power delivered from a source ofAC power to a lighting load. As shown, the dimmer switch 10 includes afaceplate 12, a bezel 14, an intensity selection actuator 16 forselecting a desired level of light intensity of a lighting load (notshown) controlled by the dimmer switch 10, and a control switch actuator18. Actuation of the upper portion 16A of the intensity selectionactuator 16 increases or raises the light intensity of the lightingload, while actuation of the lower portion 16B of the intensityselection actuator 16 decreases or lowers the light intensity. Theintensity selection actuator 16 may control a rocker switch, twoseparate push switches, or the like. The control switch actuator 18 maycontrol a push switch or any other suitable type of actuator andtypically provides tactile and auditory feedback to a user when pressed.

The smart dimmer 10 also includes an intensity level indicator in theform of a plurality of light sources 20, such as light-emitting diodes(LEDs). Light sources 20 may be arranged in an array (such as a lineararray as shown) representative of a range of light intensity levels ofthe lighting load being controlled. The intensity level of the lightingload may range from a minimum intensity level, which is preferably thelowest visible intensity, but which may be zero, or “full off,” to amaximum intensity level, which is typically “full on.” Light intensitylevel is typically expressed as a percentage of full intensity. Thus,when the lighting load is on, light intensity level may range from 1% to100%.

By illuminating a selected one of the light sources 20 depending uponlight intensity level, the position of the illuminated light sourcewithin the array provides a visual indication of the light intensityrelative to the range when the lamp or lamps being controlled are on.For example, seven LEDs are illustrated in FIG. 1. Illuminating theuppermost LED in the array will give an indication that the lightintensity level is at or near maximum. Illuminating the center LED willgive an indication that the light intensity level is at about themidpoint of the range. In addition, when the lamp or lamps beingcontrolled are off, all of the light sources 18 are illuminated at a lowlevel of illumination, while the LED representative of the presentintensity level in the on state is illuminated at a higher illuminationlevel. This enables the light source array to be more readily perceivedby the eye in a darkened environment, which assists a user in locatingthe switch in a dark room, for example, in order to actuate the switchto control the lights in the room, and provides sufficient contrastbetween the level-indicating LED and the remaining LEDs to enable a userto perceive the relative intensity level at a glance. Further, themagnitude of the low level of illumination that the LEDs are controlledto when the lighting load is off is determined such that the lightsources 18 are bright enough to be visible in direct sunlight.

According to the present invention, a control structure for anelectrical control system for producing a variable output electricalsignal to an electrical load for controllably varying the output of saidload, comprising: (1) an enclosed volume which contains controlelectronics; (2) a cover plate on one surface of said enclosed volumehaving a planar front surface and having a rectangular opening therein;(3) a touch pad disposed in said rectangular opening and coupled to saidcontrol electronics and adapted to produce an output signal which isrelated to the position within the area of said touch pad at which saidtouch pad is touched by an operator; (4) a plurality of statusindicators; and (5) a voltage source for energizing said statusindicators, said voltage source being switchable between first andsecond conditions for illuminating said status indicators at a first andlow intensity and at a second and high intensity; said voltage sourcebeing normally switched to its said first condition for illuminatingsaid status indicators with said low intensity; and circuit meanscoupled to said touch screen for switching said voltage source to saidsecond condition for a predetermined length of time following theinitial excitation of any of said status indicators by said touchscreen, and thereafter returning said voltage source to said firstcondition.

In addition, the present invention provides a control structure for anelectrical control system for producing a variable output electricalsignal to an electrical load for controllably varying the output of saidload. The control structure comprises: (1) an enclosed volume whichcontains control electronics; (2) a cover plate on one surface of saidenclosed volume having a planar front surface and having a rectangularopening therein; (3) a transparent touch pad disposed in saidrectangular opening and coupled to said control electronics and adaptedto produce an output signal which is related to the position within thearea of said touch pad at which said touch pad is touched by anoperator; (4) a plurality of vertically arranged markers printed on saidtouch pad to serve as scale indicator; (5) a plurality of statusindicators coupled to said control electronics for illuminatingrespective discrete locations on said touch pad which lie on a linealong the length of said touch pad and in a predetermined alignment withrespective ones of said printed markers and being respectivelyilluminated adjacent the position on said touch pad at which said touchpad is touched by an operator; (6) a small marker at the bottom of saidtouch pad and in the center of the width of said touch pad for togglingsaid electrical circuit when said touch pad is touched at said smallmarker location; (7) at least a first status indicator connected to saidcontrol electronics and positioned to illuminate said small marker andwhen said touch pad is touched at said small marker to turn off saidelectrical circuit; and (8) a voltage source for energizing said statusindicators, said voltage source being switchable between first andsecond conditions for illuminating said status indicators at a first andlow intensity and at a second and high intensity, said voltage sourcebeing normally switched to said first condition for illuminating saidstatus indicators with said low intensity; and circuit means coupled tosaid touch screen for switching said voltage source to said secondcondition for a predetermined length of time following the initialexcitation of any of said status indicators by said touch screen, andthereafter returning said voltage source to said first condition.

The present invention further provides a control structure for anelectrical control system for producing a variable output electricalsignal to an electrical load for controllably varying the output of saidload. The control structure comprises: (1) an enclosed volume whichcontains control electronics; (2) an actuator; (3) a plurality of statusindicators; and (4) a voltage source for energizing said statusindicators, said voltage source being switchable between first andsecond conditions for illuminating said status indicators at a first andlow intensity and at a second and high intensity, said voltage sourcebeing normally switched to its said first condition for illuminatingsaid status indicators with said low intensity; and circuit meanscoupled to said touch screen for switching said voltage source to saidsecond condition for a predetermined length of time following theinitial excitation of any of said status indicators in response to anactuation of said actuator and thereafter returning said voltage sourceto said first condition.

Other features and advantages of the present invention will becomeapparent from the following description of the invention that refers tothe accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front view of a user interface of a prior art dimmer;

FIG. 2 is a perspective view of a touch dimmer according to the presentinvention;

FIG. 3 is a front view of the touch dimmer of FIG. 2;

FIG. 4A is a partial assembled sectional view of a bezel and a touchsensitive device of the touch dimmer of FIG. 2;

FIG. 4B is a partial exploded sectional view of the bezel and the touchsensitive device of FIG. 4A;

FIG. 5 is a cross-sectional view of the touch sensitive device;

FIG. 6 shows the force profiles of the components and a cumulative forceprofile of the touch dimmer of FIG. 2;

FIG. 7 is a simplified block diagram of the touch dimmer of FIG. 2;

FIG. 8 is a simplified schematic diagram of a stabilizing circuit and ausage detection circuit of the touch dimmer of FIG. 7 according to afirst embodiment of the present invention;

FIG. 9 is a simplified schematic diagram of an audible sound generatorof the touch dimmer of FIG. 7;

FIG. 10 is a flowchart of a touch dimmer procedure executed by acontroller of the dimmer of FIG. 2;

FIG. 11 is a flowchart of an Idle procedure of the touch dimmerprocedure of FIG. 10;

FIGS. 12A and 12B are flowcharts of an ActiveHold procedure of the touchdimmer procedure of FIG. 10;

FIG. 13 is a flowchart of a Release procedure of the touch dimmerprocedure of FIG. 10; and

FIG. 14 is a flowchart of a LED Mode procedure executed by thecontroller of the dimmer of FIG. 2.

DETAILED DESCRIPTION OF THE INVENTION

The foregoing summary, as well as the following detailed description ofthe preferred embodiments, is better understood when read in conjunctionwith the appended drawings. For the purposes of illustrating theinvention, there is shown in the drawings an embodiment that ispresently preferred, in which like numerals represent similar partsthroughout the several views of the drawings, it being understood,however, that the invention is not limited to the specific methods andinstrumentalities disclosed.

FIGS. 2 and 3 are a perspective view and a front view, respectively, ofa touch dimmer 100 according to the present invention. The dimmer 100includes a faceplate 102, i.e., a cover plate, having a planar frontsurface 103 and an opening 104. The opening 104 may define a standardindustry-defined opening, such as a traditional opening or a decoratoropening, or another uniquely-sized opening as shown in FIG. 2. A bezel106 having a planar touch sensitive front surface 108 extends throughthe opening 104 of the faceplate 102. The front surface 108 of the bezel106 is positioned immediately above a touch sensitive device 110 (shownin FIGS. 4A and 4B), such that a user of the dimmer 100 actuates thetouch sensitive element 110 by pressing the front surface 108 of thebezel 106. As shown in FIG. 2, the front surface 108 of the bezel 106 issubstantially flush with the front surface 103 of the faceplate 102,i.e., the plane of the front surface 108 of the bezel 106 is coplanarwith the plane of the front surface 103 of the faceplate 102. However,the bezel 106 may extend through the opening 104 of the faceplate 102such that the front surface 108 of the bezel is provided in a planeabove the plane of the front surface 103 of the faceplate 102. Thefaceplate 102 is connected to an adapter 109, which is connected to ayoke (not shown). The yoke is adapted to mount the dimmer 100 to astandard electrical wallbox.

The dimmer 100 further comprises a visual display, e.g., a plurality ofstatus markers 112 provided in a linear array along an edge of the frontsurface 108 of the bezel 106. The status markers 112 are preferablyilluminated from behind by status indicators 114, e.g., light-emittingdiodes (LEDs), located internal to the dimmer 100 (see FIG. 7). Thedimmer 100 preferably comprises a light pipe (not shown) having aplurality of light conductors to conduct the light from the statusindicators 114 inside the dimmer to the markers 112 on the front surface108 of the bezel 106. The status indicators 114 behind the markers 112are preferably blue. As shown in FIGS. 2 and 3, the dimmer 100 comprisesseven (7) status markers 112. However, the dimmer 100 may comprise anynumber of status markers. Further, the status markers 112 may bedisposed in a vertical linear array along the center of the frontsurface 108 of the bezel 106. The markers 112 may comprise shadowsapparent on the front surface 108 due to voids behind the front surface.

Preferably, the status markers are illuminated to display the intensityof the connected lighting load 208 (FIG. 7) as feedback to a user. Oneof the status markers 112 is illuminated depending upon light intensitylevel, such that the position of the illuminated status marker 112within the linear array provides a visual indication of the lightintensity relative to the lighting intensity range of the lighting load208. Illuminating the uppermost status marker 112 in the array will givean indication that the light intensity level is at or near maximum.Illuminating the center status marker 112 will give an indication thatthe light intensity level is at about the midpoint of the range.Further, when the lighting load 208 is off, all of the markers 112 areilluminated at a low level of illumination, while the status markerrepresentative of the present intensity level (when the lighting load ison) is illuminated at a higher illumination level. Alternatively, aplurality of adjacent status indicators 114 could be illuminated in a“bar graph” fashion to display the intensity of the lighting load 208.For example, if the intensity is near the midpoint of the range, thelower four status indicators of the seven status indicators could beilluminated. Further, to indicate the maximum intensity, all of thestatus indicators 114 could be illuminated.

The front surface 108 of the bezel 106 further includes an icon 116. Theicon 116 may be any sort of visual marker, such as, for example, a dot.Upon actuation of the lower portion of the front surface 108 surroundingthe icon 116, the dimmer 100 causes a connected lighting load 208 (FIG.7) to change from on to off (and vice versa), i.e., to toggle.Preferably, a blue status indicator and an orange status indicator arelocated immediately behind the icon 116, such that the icon 116 isilluminated with blue light when the lighting load 208 is on andilluminated with orange light when the lighting load is off. Actuationof the upper portion of the front surface 108, i.e., above the portionsurrounding the icon 116, causes the intensity of the lighting load 208to change. The status indicators 114 behind the status markers 112 areilluminated to display the intensity of the lighting load 208. Forexample, if the lighting load 208 is at 50% lighting intensity, themiddle status indicator will be illuminated. Preferably, the dimmer 100does not respond to actuations in a keepout region 118 of the frontsurface 108. The keepout region 118 prevents inadvertent actuation of anundesired portion of the front surface 108 during operation of thedimmer 100.

According to the present invention, the dimmer 100 uses an “LED mode” tocontrol the intensity of the status indicators 114. When a user actuatesthe touch sensitive device 110, the dimmer 100 temporarily enters anactive LED mode, in which the status indicators 114 are illuminated to abright Active level, such that the light illuminating the status markers112 is viewable in directs sunlight, e.g., 500 footcandles. Accordingly,the dimmer 100 “wakes up”, i.e., the active LED mode is initiated, inresponse to an actuation of the touch sensitive device 110. After apredetermined period of time t_(ACTIVE), e.g., 5 seconds, after the userstops actuating, i.e., releases, the touch sensitive device 110, thedimmer 100 enters the inactive LED mode and the status indicators areilluminated to a dim Idle level. At this time, if the lighting load 208in on, the light illuminating the dimly lit status markers 112 areviewable in less than 10 footcandles and the light illuminating theintensity level status indicator is viewable in less than 250footcandles. Further, when the lighting load 208 toggled off and thedimmer 100 is in the inactive LED mode, the status indicators 114 areilluminated to a dim Off level, which is lower in intensity than the dimIdle level. Preferably, the status indicators 114 are faded from thebright Active level to both the dim Idle level and the dim Off level.“Fading” means the status indicators 114 are dimmed over a period oftime, e.g., 0.5 seconds and 0.75 seconds for the dim Idle level and thedim Off level, respectively.

The dimmer 100 further includes an airgap switch actuator 119. Pullingthe airgap switch actuator 119 opens a mechanical airgap switch 219(FIG. 7) inside the dimmer 100 and disconnects the lighting load 208from a connected AC voltage source 204 (FIG. 7). The airgap switchactuator 119 extends only sufficiently above the front surface 103 ofthe faceplate 102 to be gripped by a fingernail of a user. Theelectronic circuitry of the dimmer 100 (to be described in greaterdetail below) is mounted on a printed circuit board (PCB) (not shown).The PCB is housed in an enclosure (not shown), i.e., an enclosed volume,which is attached to the yoke of the dimmer 100.

FIG. 4A is a partial assembled sectional view and FIG. 4B is a partialexploded sectional view of the bezel 108 and the touch sensitive device110 of the dimmer 100 according to the present invention. FIG. 5 is across-sectional view of the touch sensitive device 110, specifically, amembrane voltage divider or a resistive divider. A conductive element120 and a resistive element 122 are co-extensively supported in closeproximity by a spacing frame 124. An input voltage, V_(IN), is appliedacross the resistive element 122 to provide a voltage gradient acrossits surface. When pressure is applied at a point P along the conductiveelement 120 (by a finger or the like), the conductive element flexesdownward and electrically contacts a corresponding point along thesurface of the resistive element 122, providing an output voltage,V_(OUT), whose value is between the input voltage V_(IN) and ground.When pressure is released, the conductive element 120 recovers itsoriginal shape and becomes electrically isolated from the resistiveelement 122. The touch-operated device 110 is characterized by a contactresistance R_(CONTACT) between the conductive element 120 and theresistive element 122. The contact resistance R_(CONTACT) is dependentupon the force of the actuation of the touch-operated device 110 and istypically substantially small for a normal actuation force.

An elastomer 126 is received by an opening 128 in the rear surface ofthe bezel 106. The elastomer 126 is positioned between the bezel 106 andthe touch sensitive device 110, such that a press on the front surface108 of the bezel is transmitted to the conductive element 120 of thetouch sensitive device 110. Preferably, the elastomer 126 is made ofrubber and is 0.040″ thick. The elastomer 126 preferably has a durometerof 40 A, but may have a durometer in the range of 20 A to 80 A. Theconductive element 120 and the resistive element 122 of the touchsensitive device 110 and the elastomer 126 are preferably manufacturedfrom a transparent material such that the light from the plurality ofstatus indicators 114 inside the dimmer 100 are operable to shinethrough the touch sensitive device 110 and the elastomer 126 to frontsurface 108 of the bezel 106.

The position and size of the touch sensitive device 110 is demonstratedby the dotted line in FIG. 3. The touch sensitive device 110 has alength L₁ and a width W₁ that is larger than a length L₂ and a width W₂of the front surface 108 of the bezel 106. Accordingly, a first area A₁of the surface of touch sensitive device 110 (i.e., A₁=L₁·W₁) is greaterthan a second area A₂ of the front surface 108 of the bezel 106 (i.e.,A₂=L₂·W₂). An orthogonal projection of the second area A₂ onto the firstarea A₁ is encompassed by the first area A₁, such that a point actuationat any point on the front surface 108 of the bezel 106 is transmitted tothe conductive element 120 of the touch sensitive device 110. As shownin FIGS. 2 and 3, the length L₂ of the front surface 108 of the bezel106 is approximately four (4) times greater than the width W₂.Preferably, the length L₂ of the front surface 108 of the bezel 106 isfour (4) to six (6) times greater than the width W₂. Alternatively, thefront surface 108 of the bezel 106 may be provided in an opening of adecorator-style faceplate

FIG. 6 shows the force profiles of the components of the dimmer 100shown in FIGS. 4A and 4B and a cumulative force profile for the touchsensitive device 110 of the dimmer 100. Each of the force profiles showsthe force required to actuate the touch sensitive device 110 withrespect to the position of the point actuation. The force profilerepresents the amount of force required to displace the element by agiven amount. While the force profiles in FIG. 6 are shown with respectto the widths of the components of the dimmer 100, a similar forceprofile is also provided along the length of the components.

FIG. 6( a) shows a force profile of the bezel 106. The bezel 106 hassubstantially thin sidewalls 129, e.g., 0.010″ thick, such that thebezel 106 exhibits a substantially flat force profile. FIG. 6( b) showsa force profile of the touch sensitive device 110. The force required toactuate the touch sensitive device 110 increases near the edges becauseof the spacing frames 124. FIG. 6( c) shows a force profile of theelastomer 126. The force profile of the elastomer 126 is substantiallyflat, i.e., a force at any point on the front surface of the elastomer126 will result in a substantially equal force at the correspondingpoint on the rear surface.

FIG. 6( d) is a total force profile of the touch dimmer 100. Theindividual force profiles shown in FIGS. 6( a)-6(c) are additive tocreate the total force profile. The total force profile is substantiallyflat across the second area A₂ of the front surface 108 of the bezel106. This means that a substantially equal minimum actuation forcef_(MIN) is required to actuate the touch sensitive device 110 at allpoints of the front surface 108 of the bezel 106, even around the edges.Accordingly, the dimmer 100 of the present invention provides a maximumoperational area in an opening of a faceplate, i.e., substantially allof the second area A₂ of the front surface 108 of the bezel 106, whichis an improvement over the prior art touch dimmers. The minimumactuation force f_(MIN) is substantially equal at all points on thefront surface 108 of the bezel 106. For example, the minimum actuationforce f_(MIN) may be 20 grams.

Since the force profile of the bezel 106 shown in FIG. 6( a) and theforce profile of the elastomer 126 shown in FIG. 6( c) havesubstantially small minimum actuation forces, the minimum actuationforce f_(MIN) of the total force profile of the touch dimmer 100 issubstantially equal to the minimum force of the force profile of thetouch sensitive device 110. Accordingly, the minimum actuation forcef_(MIN) of the total force profile is dependent on the selection of thetouch sensitive device 110 to be used in the dimmer 100.

FIG. 7 is a simplified block diagram of the touch dimmer 100 accordingto the present invention. The dimmer 100 has a hot terminal 202connected to an AC voltage source 204 and a dimmed hot terminal 206connected to a lighting load 208. The dimmer 100 employs a bidirectionalsemiconductor switch 210 coupled between the hot terminal 202 and thedimmed hot terminal 206, to control the current through, and thus theintensity of, the lighting load 208. The semiconductor switch 210 has acontrol input (or gate), which is connected to a gate drive circuit 212.The input to the gate renders the semiconductor switch 210 selectivelyconductive or non-conductive, which in turn controls the power suppliedto the lighting load 208. The gate drive circuit 212 provides a controlinput to the semiconductor switch 210 in response to a control signalfrom a controller 214. The controller 214 may be any suitablecontroller, such as a microcontroller, a microprocessor, a programmablelogic device (PLD), or an application specific integrated circuit(ASIC).

A zero-crossing detect circuit 216 determines the zero-crossing pointsof the AC source voltage from the AC power supply 204. A zero-crossingis defined as the time at which the AC supply voltage transitions frompositive to negative polarity, or from negative to positive polarity, atthe beginning of each half-cycle. The zero-crossing information isprovided as an input to the controller 214. The controller 214 generatesthe gate control signals to operate the semiconductor switch 210 to thusprovide voltage from the AC power supply 204 to the lighting load 208 atpredetermined times relative to the zero-crossing points of the ACwaveform. A power supply 218 generates a direct-current (DC) voltageV_(CC), e.g., 5 volts, to power the controller 214 and other low voltagecircuitry of the dimmer 100.

The touch sensitive device 110 is coupled to the controller 214 througha stabilizing circuit 220 and a usage detection circuit 222. Thestabilizing circuit 220 is operable to stabilize the voltage output ofthe touch sensitive device 110. Accordingly, the voltage output of thestabilizing circuit 220 is not dependent on the magnitude of the forceof the point actuation on the touch sensitive device 110, but rather isdependent solely on the position of the point actuation. The usagedetection circuit 222 is operable to detect when a user is actuating thefront surface 108 of the dimmer 100. The controller 214 is operable tocontrol the operation of the stabilizing circuit 220 and the usagedetection circuit 222 and to receive control signals from both thestabilizing circuit and the usage detection circuit. Preferably, thestabilizing circuit 220 has a slow response time, while the usagedetection circuit 222 has a fast response time. Thus, the controller 214is operable to control the semiconductor switch 210 in response to thecontrol signal provided by the stabilizing circuit 220 when the usagedetection circuit 222 has detected an actuation of the touch sensitivedevice 110.

The controller 214 is operable to drive the plurality of statusindicators 114, e.g., light-emitting diodes (LEDs), which are locatedbehind the markers 112 on the front surface 108 of the dimmer 100. Thestatus indicators 114 also comprise the blue status indicator and theorange status indicator that are located immediately behind the icon116. The blue status indicator and the orange status indicator may beimplemented as separate blue and orange LEDs, respectively, or as asingle bi-colored LED.

The dimmer 100 further comprises an audible sound generator 224 coupledto the controller 214, such that the controller is operable to cause thesound generator to produce an audible sound in response to an actuationof the touch sensitive device 110. A memory 225 is coupled to thecontroller 214 and is operable to store control information of thedimmer 100.

FIG. 8 is a simplified schematic diagram of the circuitry for the touchsensitive device 110 and the controller 214, i.e., the stabilizingcircuit 220 and the usage detection circuit 222, according to a firstembodiment of the present invention. The resistive element 122 of thetouch sensitive device 110 is coupled between the DC voltage V_(CC) ofthe power supply 218 and circuit common, such that the DC voltage V_(CC)provides a biasing voltage to the touch sensitive device. The resistanceof the resistive element 122 may be, for example, 7.6 kΩ. The positionof contact between the conductive element 120 and the resistive element122 of the touch sensitive device 110 is determined by the position of apoint actuation on the front surface 108 of the bezel 106 of the dimmer100. The conductive element 120 is coupled to both the stabilizingcircuit 220 and the usage detection circuit 222. As shown in FIG. 7, thetouch sensitive device 110 of the dimmer 100 of the first embodiment isa three-wire device, i.e., the touch sensitive device has threeconnections or electrodes. The touch sensitive device provides oneoutput that is representative of the position of the point actuationalong a Y-axis, i.e., a longitudinal axis of the dimmer 100 as shown inFIG. 3.

The stabilizing circuit 220 comprises a whacking-grade capacitor C230(that is, a capacitor having a large value of capacitance) and a firstswitch 232. The controller 214 is operable to control the first switch232 between a conductive state and a non-conductive state. When thefirst switch 232 is conductive, the capacitor C230 is coupled to theoutput of the touch sensitive device 110, such that the output voltageis filtered by the capacitor C230. When a touch is present, the voltageon the capacitor C230 will be forced to a steady-state voltagerepresenting the position of the touch on the front surface 108. When notouch is present, the voltage on the capacitor will remain at a voltagerepresenting the position of the last touch. The touch sensitive device110 and the capacitor C230 form a sample-and-hold circuit. The responsetime of the sample-and-hold circuit is determined by a resistance R_(D)of the touch sensitive device (i.e., the resistance R_(E) of theresistive element and a contact resistance R_(C)) and the capacitance ofthe capacitor C230. During typical actuation, the contact resistanceR_(C) is small compared to the value of R_(E), such that a firstcharging time constant τ₁ is approximately equal to R_(E)·C₂₃₀. Thistime constant τ₁ is preferably 13 ms, but may be anywhere between 6 msand 15 ms.

When a light or transient press is applied to the touch sensitive device110, the capacitor C230 will continue to hold the output at the voltagerepresenting the position of the last touch. During the release of thetouch sensitive device 110, transient events may occur that produceoutput voltages that represent positions other than the actual touchposition. Transient presses that are shorter than the first chargingtime constant τ₁ will not substantially affect the voltage on thecapacitor C230, and therefore will not substantially affect the sensingof the position of the last actuation. During a light press, a secondcharging time constant τ₂ will be substantially longer than duringnormal presses, i.e., substantially larger than the first time constantτ₁, due to the higher contact resistance R_(C). However, thesteady-state value of the voltage across the capacitor C230 will be thesame as for a normal press at the same position. Therefore, the outputof the stabilizing circuit 220 is representative of only the position ofthe point of actuation of the touch sensitive device 110.

The usage detection circuit 222 comprises a resistor R234, a capacitorC236, and a second switch 238, which is controlled by the controller214. When the switch 238 is conductive, the parallel combination of theresistor R234 and the capacitor C236 is coupled to the output of thetouch sensitive device 110. Preferably, the capacitor C236 has asubstantially small capacitance C₂₃₆, such that the capacitor C236charges substantially quickly in response to all point actuations on thefront surface 108. The resistor R234 allows the capacitor C236 todischarge quickly when the switch 238 is non-conductive. Therefore, theoutput of the usage detection circuit 222 is representative of theinstantaneous usage of the touch sensitive device 110.

The controller 214 controls the switches 232, 238 in a complementarymanner. When the first switch 232 is conductive, the second switch 238is non-conductive, and vice versa. The controller 214 controls thesecond switch 238 to be conductive for a short period of time t_(USAGE)once every half cycle of the voltage source 204 to determine whether theuser is actuating the front surface 108. Preferably, the short period oftime t_(USAGE) is approximately 100 μsec or 1% of the half-cycle(assuming each half-cycle is 8.33 msec long). For the remainder of thetime, the first switch 232 is conductive, such that the capacitor C230is operable to charge accordingly. When the first switch 232 isnon-conductive and the second switch 238 is conductive, thewhacking-grade capacitor C230 of the stabilizing circuit 220 is unableto discharge at a significant rate, and thus the voltage developedacross the capacitor C230 will not change significantly when thecontroller 214 is determining whether the touch sensitive device 110 isbeing actuated through the usage detection circuit 222.

FIG. 9 is a simplified schematic diagram of the audible sound generator224 of the dimmer 100. The audible sound generator 224 uses an audiopower amplifier integrated circuit (IC) 240, for example, part numberTPA721 manufactured by Texas Instruments, Inc., to generate a sound froma piezoelectric or magnetic speaker 242. The amplifier IC 240 is coupledto the DC voltage V_(CC) (pin 6) and circuit common (pin 7) to power theamplifier IC. A capacitor C244 (preferably having a capacitance of 0.1μF) is coupled between the DC voltage V_(CC) and circuit common todecouple the power supply voltage and to ensure the output totalharmonic distortion (THD) is as low as possible.

The audible sound generator 224 receives a SOUND ENABLE signal 246 fromthe controller 214. The SOUND ENABLE signal 246 is provided to an enablepin (i.e., pin 1) on the amplifier IC 240, such that the audible soundgenerator 224 will be operable to generate the sound when the SOUNDENABLE signal is at a logic high level.

The audible sound generate 224 further receives a SOUND WAVE signal 248from the controller 214. The SOUND WAVE signal 248 is an audio signalthat is amplified by the amplifier IC 240 to generate the appropriatesound at the speaker 242. The SOUND WAVE signal 248 is first filtered bya low-pass filter comprising a resistor R250 and a capacitor C252.Preferably, the resistor R250 has a resistance of 1 kΩ and the capacitorC252 has a capacitance of 0.1 nF. The filtered signal is then passedthrough a capacitor C254 to produce an input signal V_(IN). Thecapacitor C254 allows the amplifier IC to bias the input signal V_(IN)to the proper DC level for optimum operation and preferably has acapacitance of 0.1 μF. The input signal V_(IN) is provided to a negativeinput (pin 4) of the amplifier IC 240 through a input resistor R₁. Apositive input (pin 3) of the amplifier IC 240 and with a bypass pin(pin 2) are coupled to circuit common through a bypass capacitor C256(preferably, having a capacitance of 0.1 μF).

The output signal V_(OUT) of the amplifier IC 240 is produced from apositive output (pin 5) to a negative output (pin 8) and is provided tothe speaker 242. The negative input (pin 4) is coupled to the positiveoutput (pin 5) through an output resistor R_(F). The gain of theamplifier IC 240 is set by the input resistor R₁ and the feedbackresistor R_(f), i.e.,

Gain=V _(OUT) /V _(IN)=−2(R _(F) /R ₁).

Preferably, the input resistor R₁ and the output resistor R_(F) bothhave resistances of 10 kΩ, such that the gain of the amplifier IC 240 isnegative two (−2).

FIG. 10 is a flowchart of a touch dimmer procedure 300 executed by thecontroller 214 of the dimmer 100 according to the present invention.Preferably, the touch dimmer procedure 300 is called from the main loopof the software of the controller 214 once every half cycle of the ACvoltage source 204. The touch dimmer procedure 300 selectively executesone of three procedures depending upon the state of the dimmer 100. Ifthe dimmer 100 is in an “Idle” state (i.e., the user is not actuatingthe touch sensitive device 110) at step 310, the controller 214 executesan Idle procedure 400. If the dimmer 100 is in an “ActiveHold” state(i.e., the user is presently actuating the touch sensitive device 110)at step 320, the controller 214 executes an ActiveHold procedure 500. Ifthe dimmer 100 is in a “Release” state (i.e., the user has recentlyceased actuating the touch sensitive device 110) at step 330, thecontroller 214 executes a Release procedure 600.

FIG. 11 is a flowchart of the Idle procedure 400 according to thepresent invention. The controller 114 uses a “sound flag” and a “soundcounter” to determine when to cause the audible sound generator 224 togenerate the audible sound. The purpose of the sound flag is to causethe sound to be generated the first time that the controller 214executes the ActiveHold procedure 500 after being in the Idle state. Ifthe sound flag is set, the controller 214 will cause the sound to begenerated. The sound counter is used to ensure that the controller 214does not cause the audible sound generator 224 to generate the audiblesound too often. The sound counter preferably has a maximum soundcounter value S_(MAX), e.g., approximately 425 msec. Accordingly, thereis a gap of approximately 425 msec between generations of the audiblesound. The sound counter is started during the Release procedure 600 aswill be described in greater detail below. Referring to FIG. 11, uponentering the Idle state, the controller 214 sets the sound flag at step404 if the sound flag is not set at step 402.

An “LED counter” and the LED modes (i.e., the active LED mode and theinactive LED mode) are used by the controller 214 to control the statusindicators 114 of the dimmer 100. The controller 214 uses the LEDcounter to determine when a predetermined time t_(ACTIVE) has expiredsince the touch sensitive device 110 was actuated. When thepredetermined time t_(ACTIVE) has expired, the controller 214 willchange the LED mode from “active” to “inactive”. When the LED mode is“active”, the status indicators 114 are controlled such that one or moreof the status indicators are illuminated to a bright Active level. Whenthe predetermined time t_(ACTIVE) expires, the LED mode is changed to“inactive”, i.e., the status indicators 114 are controlled such that oneor more of the status indicators are faded to a dim Idle level, i.e.,the intensity of the status indicators is reduced to the dim Idle levelslowly over a period of time. Referring to FIG. 11, if the LED counteris less than a maximum LED counter value L_(MAX) at step 410, the LEDcounter is incremented at step 412 and the process moves on to step 418.However, if the LED counter is not less than the maximum LED countervalue L_(MAX), the LED counter is cleared at step 414 and the LED modeis set to inactive at step 416. Since the touch dimmer procedure 300 isexecuted once every half cycle, the predetermined time t_(ACTIVE) isequal to

t _(ACTIVE) =T _(HALF) ·L _(MAX),

where T_(HALF) is the period of a half cycle. For example, thepredetermined time t_(ACTIVE) may be 4 to 5 seconds.

Next, the controller 214 reads the output of the usage detection circuit222 to determine if the touch sensitive device 110 is being actuated.Preferably, the usage detection circuit 222 is monitored once every halfcycle of the voltage source 204. At step 418, the controller 214 opensswitch 232 and closes switch 238 to couple the resistor R234 and thecapacitor C236 to the output of the touch sensitive device 110. Thecontroller 214 determines the DC voltage of the output of the usagedetection circuit 222 at step 420, preferably, by using ananalog-to-digital converter (ADC). Next, the controller 214 closesswitch 232 and opens switch 238 at step 422.

At step 424, if there is activity on the front surface 108 of the dimmer100, i.e., if the DC voltage determined at step 420 is above apredetermined minimum voltage threshold, then an “activity counter” isincremented at step 426. Otherwise, the activity counter is cleared atstep 428. The activity counter is used by the controller 214 todetermine if the DC voltage determined at step 420 is the result of apoint actuation of the touch sensitive device 110 rather than noise orsome other undesired impulse. The use of the activity counter is similarto a software “debouncing” procedure for a mechanical switch, which iswell known in the art. If the activity counter is not less than amaximum activity counter value A_(MAX) at step 430, then the dimmerstate is set to the ActiveHold state at step 432. Otherwise, the processsimply exits at step 434.

FIGS. 12A and 12B are flowcharts of the ActiveHold procedure 500, whichis executed once every half cycle when the touch sensitive device 110 isbeing actuated, i.e., when the dimmer 100 is in the ActiveHold state.First, a determination is made as to whether the user has stopped using,i.e., released, the touch sensitive device 110. The controller 214 opensswitch 232 and closes switch 238 at step 510, and reads the output ofthe usage detection circuit 222 at step 512. At step 514, the controller214 closes switch 232 and opens switch 238. If there is no activity onthe front surface 108 of the dimmer 100 at step 516, the controller 214increments an “inactivity counter” at step 518. The controller 214 usesthe inactivity counter to make sure that the user is not actuating thetouch sensitive device 110 before entering the Release mode. If theinactivity counter is less than a maximum inactivity counter valueI_(MAX) at step 520, the process exits at step 538. Otherwise, thedimmer state is set to the Release state at step 522, and then theprocess exits.

If there is activity on the touch sensitive device 110 at step 516, thecontroller 214 reads the output of the stabilizing circuit 220, which isrepresentative of the position of the point actuation on the frontsurface 108 of the dimmer 100. Since the switch 232 is conductive andthe switch 238 is non-conductive, the controller 214 determines the DCvoltage at the output of the stabilizing circuit 220, preferably usingan ADC, at step 524.

Next, the controller 214 uses a buffer to “filter” the output ofstabilizing circuit 220. When a user actuates the touch sensitive device110, the capacitor C230 will charge to approximately the steady-statevoltage representing the position of the actuation on the front surface108 across a period of time determined by the first time constant τ₁ aspreviously described. Since the voltage across the capacitor C230, i.e.,the output of the stabilizing circuit 220, is increasing during thistime, the controller 214 delays for a predetermined period of time atstep 525, preferably, for approximately three (3) half cycles.

When a user's finger is removed from the front surface 108 of the bezel106, subtle changes in the force and position of the point actuationoccur, i.e., a “finger roll-off” event occurs. Accordingly, the outputsignal of the touch sensitive device 110 is no longer representative ofthe position of the point actuation. To prevent the controller 214 fromprocessing reads during a finger roll-off event, the controller 214saves the reads in the buffer and processes the reads with a delay,e.g., six half cycles later. Specifically, when the delay is over atstep 525, the controller 214 rotates the new read (i.e., from step 524)into the buffer at step 526. If the buffer has at least six reads atstep 528, the controller 214 averages the reads in the fifth and sixthpositions in the buffer at step 530 to produce the touch position data.In this way, when the user stops actuating the touch sensitive device110, the controller 214 detects this change at step 516 and sets thedimmer state to the Release state at step 522 before the controllerprocesses the reads saved in the buffer near the transition time of thetouch sensitive device.

At step 532, the controller 114 determines if the touch position datafrom step 530 is in the keepout region 118 (as shown in FIG. 3). If thetouch position data is in the keepout region 118, the ActiveHoldprocedure 500 simply exits at step 538. Otherwise, a determination ismade at step 534 as to whether the sound should be generated.Specifically, if the sound flag is set and if the sound counter hasreached a maximum sound counter value S_(MAX), the controller 214 drivesthe SOUND ENABLE signal 246 high and provides the SOUND WAVE signal 248to the audible sound generator 224 to generate the sound at step 535.Further, the sound flag is cleared at step 536 such that the sound willnot be generated as long as the dimmer 100 remains in the ActiveHoldstate.

If the touch position data is in the toggle area, i.e., the lowerportion of the front surface 108 of the bezel 106 surrounding the icon116 (as shown in FIG. 2), at step 540, the controller 214 processes theactuation of the touch sensitive device 110 as a toggle. If the lightingload 208 is presently off at step 542, the controller 214 turns thelighting load on. Specifically, the controller 214 illuminates the icon116 with the blue status indicator at step 544 and dims the lightingload 208 up to the preset level, i.e., the desired lighting intensity ofthe lighting load, at step 546. If the lighting load is presently on atstep 542, the controller 214 turns on the orange status indicator behindthe icon 116 at step 548 and fades the lighting load 208 to off at step550.

If the touch position data is not in the toggle area at step 540, thecontroller 214 scales the touch position data at step 552. The output ofthe stabilizing circuit 220 is a DC voltage between a maximum value,i.e., substantially the DC voltage V_(CC), and a minimum value, whichcorresponds to the DC voltage providing by the touch sensitive device110 when a user is actuating the lower end of the upper portion of thefront surface 108 of the bezel 106. The controller 214 scales this DCvoltage to be a value between off (i.e., 1%) and full intensity (i.e.,100%) of the lighting load 208. At step 554, the controller 214 dims thelighting load 208 to the scaled level produced in step 552.

Next, the controller 214 changes the status indicators 114 locatedbehind the markers 112 on the front surface 108 of the bezel 106. As auser actuates the touch sensitive device 110 to change intensity of thelighting load 208, the controller 214 decides whether to change thestatus indicator 114 that is presently illuminated. Since there areseven (7) status indicators to indicate an intensity between 1% and100%, the controller 214 may illuminate the first status indicator,i.e., the lowest status indicator, to represent an intensity between 1%and 14%, the second status indicator to represent an intensity between15% and 28%, and so on. The seventh status indicator, i.e., the higheststatus indicator, may be illuminated to represent an intensity between85% and 100%. Preferably, the controller 214 uses hysteresis to controlthe status indicators 114 such that if the user actuates the frontsurface 108 at a boundary between two of the regions of intensitiesdescribed above, consecutive status indicators do not toggle back andforth.

Referring to FIG. 12B, a determination is made as to whether a change isneeded as to which status indicator is illuminated at step 556. If thepresent LED (in result to the touch position data from step 530) is thesame as the previous LED, then no change in the LED is required. Thepresent LED is set the same as the previous LED at step 558, ahysteresis counter is cleared at step 560, and the process exits at step570.

If the present LED is not the same as the previous LED at step 556, thecontroller 214 determines if the LED should be changed. Specifically, atstep 562, the controller 214 determines if present LED would change ifthe light level changed by 2% from the light level indicated by thetouch position data. If not, the hysteresis counter is cleared at step560 and the process exits at step 570. Otherwise, the hysteresis counteris incremented at step 564. If the hysteresis counter is less than amaximum hysteresis counter value H_(MAX) at step 566, the process exitsat step 570. Otherwise, the LEDs are changed accordingly based on thetouch position data at step 568.

FIG. 13 is a flowchart of the Release procedure 600, which is executedafter the controller 214 sets the dimmer state to the Release state atstep 522 of the ActiveHold procedure 500. First, a save flag is set atstep 610. Next, the sound counter is reset at step 612 to ensure thatthe sound will not be generated again, e.g., for preferably 18 halfcycles. At step 618, a determination is made as to whether the dimmer100 is presently executed a fade-to-off. If not, the present level issaved as the preset level in the memory 225 at step 620. Otherwise, thedesired lighting intensity is set to off at step 622, the long fadecountdown in started at step 624, and the preset level is saved as offin the memory 225.

FIG. 14 is a flowchart of a LED Mode procedure 700 that is preferablyexecuted once every line cycle of the AC power source. At step 710, thecontroller 214 determines the correct pattern of the status indicators114, i.e., which status indicator should be illuminated greater than theother status indicators. If the dimmer 100 is in the inactive LED modeat step 712 and if the lighting load 208 is on at step 714, adetermination is made at step 716 as to whether the LEDs are presentlyat the desired intensity level, i.e., the dim Idle level. If not, theintensity of the LEDs is decreased by a predetermined step at 718. Ifthe lighting load 208 is not on at step 714 and if the LEDs are not atthe dim Off level at step 720, the intensity of the LEDs is decreased bythe predetermined step at step 718. Preferably, the predetermined stepis sized such that the LEDs fade to the dim Idle level overapproximately 0.5 seconds and to the dim Off level over approximately0.75 seconds.

While the present invention has been described as implemented in thetouch dimmer 100, the present invention may be applied to any sort ofdimmer or load control device comprising a plurality of statusindicators.

Although the present invention has been described in relation toparticular embodiments thereof, many other variations and modificationsand other uses will become apparent to those skilled in the art. It ispreferred, therefore, that the present invention be limited not by thespecific disclosure herein, but only by the appended claims.

1. A load control device for controlling the amount of power deliveredfrom an AC power source to an electrical load, the load control devicecomprising: a bidirectional semiconductor switch operable to be coupledin series electrical connection between the source and the load, thesemiconductor switch having a control input; a controller operativelycoupled to the control input of the semiconductor switch for controllingthe amount of power delivered to the load; an actuator operativelycoupled to the controller such that the controller is operable todetermine a desired amount of power to be delivered to the load inresponse to actuations of the actuator; and a visual display responsiveto the controller; wherein the controller is operable to illuminate thevisual display to a first intensity upon actuation of the actuator andto subsequently illuminate the visual display to a second intensity lessthan the first intensity after a predetermined amount of time haselapsed since the actuation of the actuator.
 2. The load control deviceof claim 1, wherein the visual display comprises a linear array ofstatus indicators.
 3. The load control device of claim 2, wherein thecontroller is operable to illuminate the linear array of statusindicators to display a representation of the desired amount of power tobe delivered to the load.
 4. The load control device of claim 3, whereinthe controller is operable to illuminate a plurality of adjacent statusindicators of the linear array to the first intensity to represent thedesired amount of power to be delivered to the load upon actuation ofthe actuator, and to subsequently illuminate the plurality of adjacentstatus indicators of the linear array to the second intensity torepresent the desired amount of power to be delivered to the load afterthe predetermined amount of time has elapsed since the actuation of theactuator.
 5. The load control device of claim 4, wherein the controlleris operable to illuminate the plurality of adjacent status indicators ofthe linear array to a third intensity less than the first and secondintensities when the lighting load is off.
 6. The load control device ofclaim 3, wherein the controller is operable to illuminate one of thelinear array of status indicators to the first intensity to representthe desired amount of power to be delivered to the load upon actuationof the actuator, and to subsequently illuminate the one of the lineararray of status indicators to the second intensity to represent thedesired amount of power to be delivered to the load after thepredetermined amount of time has elapsed since the actuation of theactuator.
 7. The load control device of claim 2, wherein the lineararray of status indicators is arranged behind the actuator such that thestatus indicators shine through the actuator.
 8. The load control deviceof claim 7, wherein the actuator comprises a touch sensitive deviceresponsive to a plurality of point actuations at a touch sensitive frontsurface of the load control device, each of the plurality of pointactuations characterized by a position and a force, the touch sensitivedevice having an output operatively coupled to the controller forproviding a control signal representative of the position of the pointactuation.
 9. The load control device of claim 2, wherein the statusindicators comprise light-emitting diodes.
 10. The load control deviceof claim 1, wherein the first intensity has a magnitude that allows thevisual display to be viewed in direct sunlight.
 11. The load controldevice of claim 10, wherein the first intensity allows the visualdisplay to be viewed in approximately 500 footcandles.
 12. The loadcontrol device of claim 11, wherein the second intensity allows thevisual display to be viewed in less than approximately 250 footcandles.13. The load control device of claim 1, wherein the intensity of thevisual display is reduced from the first intensity to the secondintensity over a period of time.
 14. The load control device of claim13, wherein the period of time is approximately 0.5 seconds.
 15. Theload control device of claim 1, wherein the actuation lasts for a periodof time between a press and a release of the actuator, and thecontroller is operable to illuminate the visual display to the firstintensity during the period of time between the press and the release ofthe actuator and for to the predetermined amount of time after therelease of the actuator.
 16. The load control device of claim 1, whereinthe predetermined amount of timer is approximately 5 seconds.
 17. Theload control device of claim 1, wherein the controller is operable toilluminate the visual display to represent the desired amount of powerto be delivered to the load.
 18. A method of displaying feedback on aplurality of status indicators of a load control device, the loadcontrol device operable to control the amount of power delivered from anAC power source to an electrical load, the method comprising the stepsof: pressing an actuator; subsequently releasing the actuator;illuminating the status indicators to a first intensity in response tothe step of pressing the actuator; and illuminating the statusindicators to a second intensity less than the first intensity after apredetermined amount of time has elapsed since the step of releasing theactuator.
 19. The method of claim 18, further comprising the step of:illuminating the status indicators to represent the amount of powerdelivered to the load.
 20. The method of claim 19, further comprisingthe steps of: illuminating a plurality of adjacent status indicators tothe first intensity to represent the desired amount of power to bedelivered to the load in response to the step of pressing the actuator;and illuminating the plurality of adjacent status indicators to the tothe second intensity to represent the desired amount of power to bedelivered to the load after the predetermined amount of time has elapsedsince the step of releasing the actuator.
 21. The method of claim 19,further comprising the steps of: illuminating one of the statusindicators to the first intensity to represent the desired amount ofpower to be delivered to the load in response to the step of pressingthe actuator; and illuminating the one of the status indicators to theto the second intensity to represent the desired amount of power to bedelivered to the load after the predetermined amount of time has elapsedsince the step of releasing the actuator.
 22. The method of claim 18,further comprising the step of: reducing the intensity of the statusindicators from the first intensity to the second intensity over aperiod of time.
 23. The method of claim 22, wherein the period of timeis approximately 0.5 seconds.
 24. The method of claim 18, furthercomprising the step of: illuminating the status indicators to a thirdintensity less than the first and second intensities when the lightingload is off.
 25. The method of claim 18, wherein the predeterminedamount of timer is approximately 5 seconds.